U.S. patent application number 15/752679 was filed with the patent office on 2019-01-24 for control device for power steering device, and power steering device.
This patent application is currently assigned to HITACHI AUTOMOTIVE SYSTEMS, LTD.. The applicant listed for this patent is HITACHI AUTOMOTIVE SYSTEMS, LTD.. Invention is credited to Shigehisa AOYAGI, Takumi HISAZUMI, Mitsuo SASAKI.
Application Number | 20190023309 15/752679 |
Document ID | / |
Family ID | 58239678 |
Filed Date | 2019-01-24 |
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United States Patent
Application |
20190023309 |
Kind Code |
A1 |
SASAKI; Mitsuo ; et
al. |
January 24, 2019 |
CONTROL DEVICE FOR POWER STEERING DEVICE, AND POWER STEERING
DEVICE
Abstract
A power steering device includes a steering mechanism, an
electric motor for applying a steering assist force to the steering
mechanism, and a first motor rotational position sensor for sensing
as an actual axis phase a rotational position of a rotor of the
electric motor. A control device is configured to: receive input of
a signal of first actual axis phase outputted from the first motor
rotational position sensor; receive input of a signal of value of
electric current flowing through the electric motor; estimate as a
control phase a phase of an induced voltage occurring in the
electric motor, based on the signal of value of electric current;
and determine whether or not the first motor rotational position
sensor is abnormal, based on a difference between the first actual
axis phase and the control phase.
Inventors: |
SASAKI; Mitsuo; (Hadano-shi,
Kanagawa, JP) ; HISAZUMI; Takumi; (Atsugi-shi,
Kanagawa, JP) ; AOYAGI; Shigehisa; (Mito-shi,
Ibaraki, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI AUTOMOTIVE SYSTEMS, LTD. |
Hitachinaka-shi, Ibaraki |
|
JP |
|
|
Assignee: |
HITACHI AUTOMOTIVE SYSTEMS,
LTD.
Hitachinaka-shi, Ibaraki
JP
|
Family ID: |
58239678 |
Appl. No.: |
15/752679 |
Filed: |
July 29, 2016 |
PCT Filed: |
July 29, 2016 |
PCT NO: |
PCT/JP2016/072288 |
371 Date: |
February 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B62D 5/046 20130101;
H02P 29/032 20160201; B62D 5/0463 20130101; H02P 6/16 20130101;
B62D 5/049 20130101 |
International
Class: |
B62D 5/04 20060101
B62D005/04; H02P 6/16 20060101 H02P006/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2015 |
JP |
2015-178051 |
Claims
1. A power steering device control device for a power steering
device, the power steering device including: a steering mechanism
configured to transmit rotation of a steering wheel to a steered
wheel; an electric motor configured to apply a steering assist
force to the steering mechanism; a transmission mechanism disposed
between the steering mechanism and the electric motor, and
configured to transmit a torque of the electric motor to the
steering mechanism; and a first motor rotational position sensor
configured to sense as an actual axis phase a rotational position
of a rotor of the electric motor; the power steering device control
device comprising: an actual axis phase signal receiving part
configured to receive input of a signal of first actual axis phase
outputted from the first motor rotational position sensor; a motor
current signal receiving part configured to receive input of a
signal of value of electric current flowing through the electric
motor; a control phase estimation part configured to estimate as a
control phase a phase of an induced voltage occurring in the
electric motor, based on the signal of value of electric current;
and a sensor abnormality determination part configured to determine
whether or not the first motor rotational position sensor is
abnormal, based on a difference between the first actual axis phase
and the control phase.
2. The power steering device control device as claimed in claim 1,
wherein: the power steering device further includes a second motor
rotational position sensor configured to sense as an actual axis
phase the rotational position of the rotor of the electric motor;
the power steering device control device further comprises a motor
drive control part configured to control driving of the electric
motor, based on the signal of first actual axis phase; and the
motor drive control part is configured to control driving of the
electric motor, based on an output signal of the second motor
rotational position sensor as a signal of second actual axis phase,
in response to a determination that the first motor rotational
position sensor is abnormal.
3. The power steering device control device as claimed in claim 2,
further comprising an actual axis phase comparison part configured
to compare the signal of first actual axis phase with the signal of
second actual axis phase, wherein the sensor abnormality
determination part is configured to determine whether or not the
first motor rotational position sensor is abnormal, based on the
difference between the first actual axis phase and the control
phase, and a result of the comparison by the actual axis phase
comparison part.
4. The power steering device control device as claimed in claim 3,
wherein the sensor abnormality determination part is configured to
determine that the first motor rotational position sensor is
abnormal, in response to a condition that a difference between the
signal of first actual axis phase and the signal of second actual
axis phase is greater than a predetermined value, and the
difference between the first actual axis phase and the control
phase is greater than a predetermined value.
5. The power steering device control device as claimed in claim 4,
wherein the sensor abnormality determination part is configured to
determine whether or not the second motor rotational position
sensor is abnormal, based on a difference between the second actual
axis phase and the control phase, when the motor drive control part
is controlling driving of the electric motor based on the signal of
second actual axis phase.
6. The power steering device control device as claimed in claim 5,
wherein the sensor abnormality determination part is configured to
start to determine whether or not the second motor rotational
position sensor is abnormal, in response to a lapse of a
predetermined time period after the motor drive control part shifts
from the drive control based on the signal of first actual axis
phase to the drive control based on the signal of second actual
axis phase.
7. The power steering device control device as claimed in claim 2,
wherein the sensor abnormality determination part is configured to
determine whether or not the second motor rotational position
sensor is abnormal, based on a difference between the second actual
axis phase and the control phase, when the motor drive control part
is controlling driving of the electric motor based on the signal of
second actual axis phase.
8. The power steering device control device as claimed in claim 2,
wherein the motor drive control part is configured to control
driving of the electric motor such that output of the electric
motor decreases, after shifting from the drive control based on the
signal of first actual axis phase to the drive control based on the
signal of second actual axis phase.
9. The power steering device control device as claimed in claim 2,
wherein the motor drive control part is configured to control
driving of the electric motor such that output of the electric
motor decreases gradually, after shifting from the drive control
based on the signal of first actual axis phase to the drive control
based on the signal of second actual axis phase.
10. The power steering device control device as claimed in claim 2,
wherein the sensor abnormality determination part is configured to
determine whether or not the first motor rotational position sensor
is abnormal, based on comparison between the difference between the
first actual axis phase and the control phase and a difference
between the second actual axis phase and the control phase.
11. The power steering device control device as claimed in claim 1,
wherein the sensor abnormality determination part is configured to
stop determining whether or not the first motor rotational position
sensor is abnormal, in response to a condition that rotational
speed of the electric motor is less than or equal to a
predetermined value.
12. The power steering device control device as claimed in claim
11, wherein the rotational speed of the electric motor is
configured to be estimated based on a signal other than the signal
outputted from the first motor rotational position sensor.
13. The power steering device control device as claimed in claim
12, further comprising a steering angle signal receiving part
configured to receive input of a signal of rotational angle of the
steering wheel as steering angle, wherein the rotational speed of
the electric motor is configured to be estimated based on the
signal of steering angle.
14. The power steering device control device as claimed in claim
13, further comprising: a torsion bar provided in the steering
mechanism; and a steering angle sensor disposed closer to the
steering wheel than the torsion bar, and configured to sense the
steering angle; wherein the rotational speed of the electric motor
is configured to be estimated depending on a quantity of torsion of
the torsion bar.
15. The power steering device control device as claimed in claim 1,
wherein the sensor abnormality determination part is configured to:
calculate the difference between the first actual axis phase and
the control phase, based on a voltage (Vdc) in a d-axis, a voltage
(Vqc) in a q-axis, a sensed electric current (Idc) in the d-axis, a
sensed electric current (Iqc) in the q-axis, and a rotational speed
(.omega.1) of the control phase, wherein the d-axis is a
pole-to-pole direction of the rotor of the electric motor, and
wherein the q-axis is perpendicular to the d-axis; and determine
whether or not the first motor rotational position sensor is
abnormal, based on a result of the calculation of the
difference.
16. The power steering device control device as claimed in claim
15, wherein the sensor abnormality determination part is configured
to calculate the difference between the first actual axis phase and
the control phase, further depending on a resistance (r) of winding
of the electric motor and an inductance (Lq) of the electric
motor.
17. The power steering device control device as claimed in claim
16, wherein the sensor abnormality determination part is configured
to calculate the difference between the first actual axis phase and
the control phase by using the following equation: .DELTA. .theta.
= tan - 1 [ Vdc - r Idc + .omega. 1 Lq Iqc Vqc - r Iqc - .omega. 1
Lq Idc ] . ##EQU00006##
18. The power steering device control device as claimed in claim
17, wherein the sensor abnormality determination part is configured
to calculate the difference between the first actual axis phase and
the control phase by using the following equation: .DELTA. .theta.
= tan - 1 [ Idc - r Vdc + .omega. 1 Lq Vqc Iqc - r Vqc - .omega. 1
Lq Vdc ] . ##EQU00007##
19. A power steering device comprising: a steering mechanism
configured to transmit rotation of a steering wheel to a steered
wheel; an electric motor configured to apply a steering assist
force to the steering mechanism; a transmission mechanism disposed
between the steering mechanism and the electric motor, and
configured to transmit a torque of the electric motor to the
steering mechanism; a first motor rotational position sensor
configured to sense as an actual axis phase a rotational position
of a rotor of the electric motor; and a control device configured
to control driving of the electric motor; the control device
including: an actual axis phase signal receiving part configured to
receive input of a signal of first actual axis phase outputted from
the first motor rotational position sensor; a motor current signal
receiving part configured to receive input of a signal of value of
electric current flowing through the electric motor; a control
phase estimation part configured to estimate as a control phase a
phase of an induced voltage occurring in the electric motor, based
on the signal of value of electric current; and a sensor
abnormality determination part configured to determine whether or
not the first motor rotational position sensor is abnormal, based
on a difference between the first actual axis phase and the control
phase.
20. The power steering device as claimed in claim 19, wherein: the
power steering device further comprises a second motor rotational
position sensor configured to sense as an actual axis phase the
rotational position of the rotor of the electric motor; the control
device further comprises a motor drive control part configured to
control driving of the electric motor, based on the signal of first
actual axis phase; and the motor drive control part is configured
to control driving of the electric motor, based on an output signal
of the second motor rotational position sensor as a signal of
second actual axis phase, in response to a determination that the
first motor rotational position sensor is abnormal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a power steering device and
a power steering device control device for application to a
vehicle.
BACKGROUND ART
[0002] A patent document 1 discloses a known conventional power
steering device control device as follows.
[0003] The power steering device control device is employed in a
power steering device, which the power steering device includes: a
steering mechanism configured to transmit rotation of a steering
wheel to steered wheels; an electric motor configured to apply a
steering assist force to the steering mechanism; and a motor
rotational position sensor configured to sense as an actual axis
phase a rotational position of a rotor of the electric motor. The
power steering device control device is configured to: sense a
phase difference between the actual axis phase and a control phase,
wherein the control phase is estimated based on a resistance, an
inductance, a sensed electric current value, and a voltage command
value of winding of the electric motor, and a steering speed; and
compensate for the phase difference, and thereby enhance the
efficiency of drive of the electric motor.
PRIOR ART DOCUMENT(S)
Patent Document(s)
[0004] Patent Document 1: JP 2006-166677 A
SUMMARY OF THE INVENTION
[0005] The conventional power steering device control device
described above is confronted by a problem that when an abnormality
such as a failure occurs in the motor rotational position sensor,
the power steering device control device may be unable to calculate
the phase difference normally, because the actual axis phase is
sensed by the motor rotational position sensor.
[0006] The present invention has been made with attention to the
technical problem described above, and is targeted for providing a
power steering device and a power steering device control device
capable of sensing abnormality of a motor rotational position
sensor.
[0007] According to the present invention, among other things, a
power steering device control device for a power steering device,
the power steering device including: a steering mechanism
configured to transmit rotation of a steering wheel to a steered
wheel; an electric motor configured to apply a steering assist
force to the steering mechanism; a transmission mechanism disposed
between the steering mechanism and the electric motor, and
configured to transmit a torque of the electric motor to the
steering mechanism; and a motor rotational position sensor
configured to sense as an actual axis phase a rotational position
of a rotor of the electric motor; the power steering device control
device comprises: a control phase estimation part configured to
estimate as a control phase a phase of an induced voltage occurring
in the electric motor, based on a signal of value of electric
current flowing through the electric motor; and a sensor
abnormality determination part configured to determine whether or
not the motor rotational position sensor is abnormal, based on a
difference between the actual axis phase and the control phase.
Effects of the Invention
[0008] The present invention makes it possible to sense abnormality
of the motor rotational position sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view showing a power steering device
according to a first embodiment of the present invention.
[0010] FIG. 2 is a longitudinal sectional view of the power
steering device.
[0011] FIG. 3 is a sectional view taken along a line A-A in FIG.
2.
[0012] FIG. 4 is a block diagram showing configuration of an
electrical system of a control device according to the first
embodiment.
[0013] FIG. 5 is a control block diagram showing configuration of a
calculating circuit of the control device according to the first
embodiment.
[0014] FIG. 6 is a diagram showing a relationship between an actual
axis phase and a control phase, and a definition of a phase
difference.
[0015] FIG. 7 is a flow chart showing an abnormality determination
processing control for a motor rotational position sensor according
to the first embodiment.
[0016] FIG. 8 is a flow chart showing an abnormality determination
processing control for a motor rotational position sensor according
to a second embodiment.
[0017] FIG. 9 is a flow chart showing an abnormality determination
processing control for a motor rotational position sensor according
to a third embodiment.
[0018] FIG. 10 is a flow chart showing an abnormality determination
processing control for a motor rotational position sensor according
to a fourth embodiment.
[0019] FIG. 11 is a control block diagram showing configuration of
a calculating circuit of a control device according to a fifth
embodiment.
[0020] FIG. 12 is a flow chart showing an abnormality determination
processing control for a motor rotational position sensor according
to the fifth embodiment.
[0021] FIG. 13 is a flow chart showing a control process performed
when one of two motor rotational position sensors becomes abnormal
in the flow chart of FIG. 12.
MODE(S) FOR CARRYING OUT THE INVENTION
[0022] The following describes a power steering device and a power
steering device control device according to embodiments of the
present invention in detail with reference to the drawings.
First Embodiment
[0023] As shown in FIGS. 1 to 3, the power steering device includes
a steering mechanism 1 and a steering assist mechanism 2, wherein
steering mechanism 1 is configured to transmit rotation of a
steering wheel not shown to steered wheels not shown, and wherein
steering assist mechanism 2 is configured to assist steering
operation of a driver by applying a steering assist force to
steering mechanism 1, based on information about steering and
others.
[0024] Steering mechanism 1 generally includes an input shaft 3, an
output shaft 5, and a rack bar 6, wherein input shaft 3 includes a
first end side linked to the steering wheel in a manner to rotate
integrally with the steering wheel, wherein output shaft 5 includes
a first end side coupled to input shaft 3 via a torsion bar 4 in a
manner to rotate with respect to input shaft 3, and wherein rack
bar 6 includes an outer periphery formed with rack teeth 6a meshed
with a pinion gear 5a of an outer periphery of a second end portion
of output shaft 5, and is configured to travel in an axial
direction of rack bar 6. Rack bar 6 includes end portions linked to
the steered wheels via tie rods 7, 7, knuckle arms not shown, etc.,
respectively, and is configured to change orientation of each
steered wheel by pulling the corresponding knuckle arm by axial
movement of rack bar 6.
[0025] A torque sensor "TS" and a steering angle sensor "AS" are
provided in a sensor housing accommodating the input shaft 3 and
output shaft 5, wherein torque sensor TS is configured to sense a
steering torque in steering mechanism 1 which is caused by driver's
steering operation, and wherein steering angle sensor AS is
configured to sense a steering angle that is a quantity of rotation
of the steering wheel from its neutral position.
[0026] Torque sensor TS is configured to calculate the steering
torque based on a difference in rotational angle between input
shaft 3 and output shaft 5 which is caused by torsion of torsion
bar 4. Torque sensor TS is disposed at input shaft 3 so as to
rotate along with input shaft 3, wherein input shaft 3 is closer to
the steering wheel than torsion bar 4 in a steering force
transmission line from the steering wheel to rack bar 6. Torque
sensor TS includes main and auxiliary torque sensors TS1, TS2 in
pairs (see FIG. 4), and is configured to sense main and auxiliary
steering torques by main and auxiliary torque sensors TS1, TS2, and
thereafter output signals of these steering torques as main and
auxiliary steering torque signals Tr(Main), Tr(Sub) to steering
torque signal receiving parts 37a, 37b in a control device 11
described below.
[0027] Steering angle sensor AS includes main and auxiliary
steering angle sensors AS1, AS2 in pairs (see FIG. 4), and is
configured to sense main and auxiliary steering angles by main and
auxiliary steering angle sensors AS1, AS2, and thereafter output
signals of these steering angles as main and auxiliary steering
angle signals .theta.s(Main), .theta.s(Sub) to steering angle
signal receiving parts 40a, 40b in control device 11.
[0028] As shown in FIG. 2, steering assist mechanism 2 includes: a
motor unit 8 configured to output a steering assist force,
depending on a result of sensing of torque sensor TS and steering
angle sensor AS; and a transmission mechanism 9 configured to
transmit the steering assist force (torque) to rack bar 6 while
converting the steering assist force into an axial moving force of
rack bar 6 with speed reduction.
[0029] Motor unit 8 is an integral unit of an electric motor 10 and
control device 11, wherein electric motor 10 is configured to
rotate an input pulley 12 described below, and thereby apply the
steering assist force to rack bar 6 via transmission mechanism 9,
and wherein control device 11 is attached to electric motor 10, and
is configured to control driving of electric motor 10 depending on
parameters such as the steering torque and vehicle speed.
[0030] Electric motor 10 is a three-phase brushless DC motor of a
so-called permanent magnet field type, wherein a housing
accommodating the electric motor 10 is provided with main and
auxiliary motor rotational position sensors PS1, PS2 in pairs (see
FIG. 4) which are first and second motor rotational position
sensors configured to sense an actual axis phase that is a
rotational position of a rotor not shown of electric motor 10.
[0031] The following describes definitions of actual axis and
actual axis phase with reference to FIG. 6.
[0032] In the present embodiment, a d-q axis coordinate system
composed of a d-axis and a q-axis, wherein the d-axis is a
pole-to-pole axis of a permanent magnet of the rotor, and the
q-axis is perpendicular to the d-axis, is referred to simply as
actual axis coordinate system or actual axes, whereas a phase of
the d-axis with respect to a U-phase winding axis of a stator not
shown of electric motor 10 is referred to as actual axis phase. The
polarity of the actual axis phase is defined to be positive when
the actual axes are rotating in a counterclockwise direction
(normal rotational direction), and be negative when the actual axes
are rotating in a clockwise direction (reverse rotational
direction).
[0033] Each motor rotational position sensor PS1, PS2 is configured
to sense the actual axis phase, and output signals of sensed first
and second actual axis phases as main and auxiliary actual axis
phase signals .theta.d(Main), .theta.d(Sub) in pairs to actual axis
phase signal receiving parts 44a, 44b described below in control
device 11.
[0034] As shown in FIG. 2, transmission mechanism 9 includes: input
pulley 12 provided at an outer peripheral side of an output shaft
10a of electric motor 10 in a manner to rotate integrally with
output shaft 10a about an axis of output shaft 10a; an output
pulley 13 provided at the outer periphery of rack bar 6 in a manner
to rotate with respect to rack bar 6, and configured to rotate
about an axis of rack bar 6 based on a torque of input pulley 12; a
ball screw mechanism 14 disposed between output pulley 13 and rack
bar 6, and configured to convert rotation of output pulley 13 into
axial movement of rack bar 6 with speed reduction; and a belt 15
wound over the input and output pulleys 12, 13, and configured to
transmit rotation of input pulley 12 to output pulley 13, and
thereby serve for synchronized rotation of input and output pulleys
12, 13.
[0035] The following describes specific configuration of control
device 11 according to the present embodiment with reference to
FIGS. 4 and 5.
[0036] As shown in FIG. 4, control device 11 includes: a power
supply circuit 21 serving as a power supply in control device 11; a
processing unit (microprocessor unit) 22 configured to be started
up by power supply from power supply circuit 21, and perform
various calculation operations; a pre-driver 23 configured as an
integrated circuit (IC) to receive input of a command signal from
processing unit 22; and an inverter circuit 24 configured to be
driven and controlled based on a command signal from pre-driver
23.
[0037] When power supply circuit 21 receives supply of electric
power from a battery "VB" in response to on-operation of an
ignition switch "IGN-SW" of the vehicle, power supply circuit 21
supplies the electric power to processing unit 22, torque sensors
TS1, TS2, steering angle sensors AS1, AS2, motor rotational
position sensors PS1, PS2, and pre-driver 23, while performing
appropriate voltage reduction.
[0038] Processing unit 22 is connected electrically to a vehicle
speed sensor 25, and is configured to receive input of a vehicle
speed signal "Vs" from vehicle speed sensor 25, wherein vehicle
speed sensor 25 is provided at a differential gear not shown or the
like.
[0039] Processing unit 22 is also connected electrically to torque
sensors TS1, TS2, steering angle sensors AS1, AS2, and motor
rotational position sensors PS1, PS2, and is configured to receive
input of main and auxiliary steering torque signals Tr(Main),
Tr(Sub) from torque sensors TS1, TS2, main and auxiliary steering
angle signals .theta.s(Main), .theta.s(Sub) from steering angle
sensors AS1, AS2, and main and auxiliary actual axis phase signals
.theta.d(Main), .theta.d(Sub) from motor rotational position
sensors PS1, PS2.
[0040] When receiving a command signal from pre-driver 23, the
inverter circuit 24 convers the electric power from battery VB from
direct current to three-phase alternating current and supply the
same to electric motor 10 in accordance with the command signal. A
failsafe circuit 26 is disposed between battery VB and inverter
circuit 24, and is configured to shut off the electric power sent
from battery VB to inverter circuit 24, based on commanding of
processing unit 22, when a failure or the like occurs in the power
steering device.
[0041] A motor current sensing part 27 is disposed at a downstream
side of inverter circuit 24, and is configured to sense an actual
motor current "Id" that is an actual current flowing through the
electric motor 10. The actual motor current Id sensed by motor
current sensing part 27 is inputted to a current monitoring circuit
28 provided in control device 11. Thereafter, actual motor current
Id is applied with high-response filter processing by main and
auxiliary current sensing circuits 29a, 29b for motor control in
pairs, and is fed back to processing unit 22, and is also applied
with low-response filter processing by main and auxiliary current
sensing circuits 29c, 29d for overcurrent sensing in pairs, and is
fed back to processing unit 22.
[0042] As shown in FIG. 5, control device 11 includes: a motor
command signal calculation part 31 configured to calculate a motor
command signal "Io" for control of driving of electric motor 10,
based on main steering torque signal Tr(Main); a motor drive
control part 32 configured to control driving of electric motor 10
by outputting a command voltage to inverter circuit 24, based on
motor command signal Io and others; a failsafe determination part
33 configured to determine whether or not a failsafe operation is
required, based on comparison between main and auxiliary sensing
signals outputted from each of the various sensors; and a failsafe
processing part 34 configured to perform various failsafe
operations, based on a result of determination by failsafe
determination part 33 and others.
[0043] Motor command signal calculation part 31 calculates a basic
signal "Ib" by using a prepared assist map 39, based on main
steering torque signal Tr(Main) inputted through steering torque
signal receiving part 37a from main torque sensor TS1, and a
vehicle speed signal Vs inputted through a vehicle speed signal
receiving part 38 from vehicle speed sensor 25. Motor command
signal calculation part 31 further includes: a steering assist
control part 41 configured to calculate a correction signal "Ic" in
parallel, based on main steering angle signal .theta.s(Main)
inputted through steering angle signal receiving part 40a from main
steering angle sensor AS1; and an adder 42 configured to calculate
motor command signal Io by adding the correction signal Ic to basic
signal Ib.
[0044] Furthermore, motor command signal calculation part 31
includes a limiter processing part 43 configured to control an
upper limit value of motor command signal Io variably. For example,
when electric motor 10 is overheated, the limiter processing part
43 sets the upper limit value of motor command signal Io lower than
in a normal state.
[0045] Motor drive control part 32 controls driving of electric
motor 10, generally based on motor command signal Io inputted from
motor command signal calculation part 31 (limiter processing part
43), and main actual axis phase signal .theta.d(Main) inputted
through actual axis phase signal receiving part 44a and a switching
part 47 described below from main motor rotational position sensor
PS1, and three-phase voltage values Vu, Vv, Vw sensed by voltage
sensors 45a-45c provided in inverter circuit 24.
[0046] In situations such as a situation where a sensor abnormality
determination part 49 described below determines that main motor
rotational position sensor PS1 is abnormal, electric motor 10 is
controlled by using the auxiliary actual axis phase signal
.theta.d(Sub) instead of main actual axis phase signal
.theta.d(Main), wherein auxiliary actual axis phase signal
.theta.d(Sub) is inputted through actual axis phase signal
receiving part 44b and switching part 47 described below from
auxiliary motor rotational position sensor PS2.
[0047] Failsafe determination part 33 is connected to a first
redundant monitoring part 46a, a second redundant monitoring part
46b, and a third redundant monitoring part 46c, wherein first
redundant monitoring part 46a is configured to monitor the main and
auxiliary steering torque signals Tr(Main), Tr(Sub) inputted
through steering torque signal receiving parts 37a, 37b, wherein
second redundant monitoring part 46b is configured to monitor the
main and auxiliary steering angle signals .theta.s(Main),
.theta.s(Sub) inputted through steering angle signal receiving
parts 40a, 40b, and wherein third redundant monitoring part 46c is
configured to monitor the main and auxiliary actual axis phase
signals .theta.d(Main), .theta.d(Sub) inputted through actual axis
phase signal receiving parts 44a, 44b.
[0048] Each redundant monitoring part 46a-46c is configured to
calculate a difference between the corresponding inputted main and
auxiliary signals, and when the difference becomes greater than or
equal to a predetermined value, assume that the corresponding
sensor becomes abnormal, and output to failsafe determination part
33 a signal indicating the occurrence of abnormality.
[0049] Failsafe processing part 34 performs a failsafe operation as
occasion arises, depending on an abnormality occurrence signal
inputted from failsafe determination part 33 or a result of
determination of sensor abnormality determination part 49 described
below, wherein the failsafe operation includes an operation to warn
a driver by turning on a warning light not shown provided on an
instrument panel of the vehicle, and an operation to activate the
switching part 47 to shift between actual axis phase signals
.theta.d(Main), .theta.d(Sub) for input to motor drive control part
32, and an operation to shut off the steering assist control
system.
[0050] Control device 11 further includes: a control phase
estimation part 48 configured to estimate as a control phase a
phase of induced voltage (control axis) occurring in electric motor
10; and sensor abnormality determination part 49 configured to
determine whether or not main and auxiliary motor rotational
position sensors PS1, PS2 are abnormal, based on a difference
between the actual axis phase and the control phase estimated by
control phase estimation part 48.
[0051] The following describes definitions of the control axis and
the control phase with reference to FIG. 6.
[0052] In the present embodiment, a dc-qc axis coordinate system
composed of a dc-axis and a qc-axis, wherein the dc-axis is a
pole-to-pole axis of a magnet of an imaginary rotor for the
control, and the qc-axis is perpendicular to the dc-axis, is
referred to simply as control axis coordinate system or control
axes, whereas a phase of the dc-axis with respect to the U-phase
winding axis of the stator not shown of electric motor 10 is
referred to as control phase. The polarity of the control phase is
defined to be positive when the control axes are rotating in a
counterclockwise direction (normal rotational direction), and be
negative when the control axes are rotating in a clockwise
direction (reverse rotational direction).
[0053] Control phase estimation part 48 is configured to: estimate
the control phase, based on: voltages Vdc, Vqc that are dc-axis and
qc-axis components of the command voltage calculated in motor drive
control part 32; electric currents Idc, Iqc that are dc-axis and
qc-axis components of actual motor current Im inputted through
motor current signal receiving part 50; a rotational speed .omega.1
of the control phase calculated based on a frequency of voltage
applied to electric motor 10; a resistance "r" of winding of
electric motor 10; and an inductance "Lq" of electric motor 10; and
output a signal of the estimated control phase as a control phase
signal .theta.dc to sensor abnormality determination part 49.
[0054] Sensor abnormality determination part 49 is configured to:
determine whether or not main motor rotational position sensor PS1
is abnormal, when motor drive control part 32 is controlling the
electric motor 10 based on main actual axis phase signal
.theta.d(Main); and determine whether or not auxiliary motor
rotational position sensor PS2 is abnormal, when motor drive
control part 32 is controlling the electric motor 10 based on
auxiliary actual axis phase signal .theta.d(Sub).
[0055] Specifically, sensor abnormality determination part 49 has a
function of calculating main and auxiliary phase differences
.DELTA..theta.(Main), .DELTA..theta.(Sub) each of which is a
difference between control phase signal .theta.dc inputted from
control phase estimation part 48 and a corresponding one of main
and auxiliary actual axis phase signals .theta.d(Main),
.theta.d(Sub) sensed by motor rotational position sensor PS1, PS2.
More specifically, main and auxiliary phase differences
.DELTA..theta.(Main), .theta..theta.(Sub) are calculated by using
the following equation (1).
.DELTA. .theta. = tan - 1 [ Vdc - r Idc + .omega. 1 Lq Iqc Vqc - r
Iqc - .omega. 1 Lq Idc ] ( 1 ) ##EQU00001##
[0056] Equation (1) is well known as an equation used for a case
where electric motor 10 is precisely controlled in sensorless
state, which is derived as disclosed specifically in patent
document 1 (JP 2006-166677 A).
[0057] More specifically, equation (1) is for calculation of main
and auxiliary phase differences .DELTA..theta.(Main),
.DELTA..theta.(Sub) in a situation where electric motor 10 is
rotating in the normal rotational direction. In a situation where
electric motor 10 is rotating in the reverse rotational direction,
main and auxiliary phase differences .DELTA..theta.(Main),
.DELTA..theta.(Sub) are calculated by using the following equation
(2), yielding the same values as calculated by using the equation
(1).
.DELTA. .theta. = tan - 1 [ ( - 1 ) ( Vdc - r Idc + .omega. 1 Lq
Iqc ) ( - 1 ) ( Vqc - r Iqc - .omega. 1 Lq Idc ) ] ( 2 )
##EQU00002##
[0058] Furthermore, main and auxiliary phase differences
.DELTA..theta.(Main), .DELTA..theta.(Sub) can be calculated by
using the following equation (3).
.DELTA. .theta. = tan - 1 [ Idc - r Vdc + .omega. 1 Lq Vqc Iqc - r
Vqc - .omega. 1 Lq Vdc ] ( 3 ) ##EQU00003##
[0059] The thus-calculated main and auxiliary phase differences
.DELTA..theta.(Main), .DELTA..theta.(Sub) are basically in a
predetermined angular range even with some errors in calculation
and some errors in attachment, when motor rotational position
sensors PS1, PS2 are attached to electric motor 10 correctly, and
are operating normally.
[0060] When the calculated phase difference .DELTA..theta.(Main),
.DELTA..theta.(Sub) is out of the predetermined angular range, the
sensor abnormality determination part 49 determines that the
corresponding motor rotational position sensor PS1, PS2 becomes
abnormal, and outputs a result of determination to failsafe
processing part 34. Failsafe processing part 34 performs various
failsafe operations depending on situations, which are described in
detail below in a section for abnormality determination control
flow for motor rotational position sensors PS1, PS2.
[0061] As generally known, when rotational speed .omega.r of
electric motor 10 (henceforth referred to simply as motor
rotational speed .omega.r) is low, namely, when rotational speed
.omega.1 of the control axis is low, a large error of calculation
occurs in the phase differences .DELTA..theta.(Main),
.DELTA..theta.(Sub) calculated by the equations (1)-(3).
[0062] In consideration of that, the sensor abnormality
determination part 49 is configured to stop determining whether or
not each motor rotational position sensor PS1, PS2 is abnormal, in
response to a condition where motor rotational speed .omega.r is
estimated and inputted by a motor rotational speed estimation part
51, and is lower than or equal to a predetermined value.
[0063] Motor rotational speed estimation part 51 is configured to:
estimate motor rotational speed .omega.r, based on steering speed
signal .omega.s, depending on a quantity of torsion of torsion bar
4, where steering speed signal .omega.s is obtained by
time-differentiation of the main steering angle signal
.theta.s(Main) inputted from steering speed calculation part 52;
and output the estimated motor rotational speed .omega.r to sensor
abnormality determination part 49.
[0064] The following describes specifically an abnormality
determination processing control for motor rotational position
sensors PS1, PS2, which is performed by control device 11 according
to the present embodiment, with reference to a flow chart shown in
FIG. 7.
[0065] Control device 11 first acquires steering speed signal
.omega.s from steering speed calculation part 52 (Step S101), and
further acquires main actual axis phase signal .theta.d(Main)
sensed by main motor rotational position sensor PS1 (Step S102).
Subsequently, control device 11 acquires auxiliary actual axis
phase signal .theta.d(Sub) sensed by auxiliary motor rotational
position sensor PS2 (Step S103), and thereafter determines whether
or not an auxiliary sensor diagnosis flag Fs described below is set
(Step S104).
[0066] In case of NO at Step S104, control device 11 determines
that abnormality determination for main motor rotational position
sensor PS1 is to be performed, and calculates phase difference
.DELTA..theta.(Main) between main actual axis phase signal
.theta.d(Main) and the control phase by using the equation (1) or
the like (Step S105), and further determines whether or not motor
rotational speed .omega.r estimated from steering speed signal
.omega.s is greater than a predetermined value .omega.x (Step
S106). In case of NO at Step S106, control device 11 terminates the
present program without diagnosis, for prevention of incorrect
diagnosis. On the other hand, in case of YES at Step S106, control
device 11 determines that the diagnosis is to be continued, and
proceeds to Step S107.
[0067] At Step S107, control device 11 determines whether or not
the phase difference .DELTA..theta.(Main) calculated at Step S105
is greater than or equal to a predetermined value .DELTA..theta.x.
In case of NO at Step S107, control device 11 determines that main
motor rotational position sensor PS1 is not abnormal, and rests the
auxiliary sensor diagnosis flag Fs (Step S111), and thereafter
terminates the present program.
[0068] On the other hand, in case of YES at Step S107, control
device 11 determines that main motor rotational position sensor PS1
becomes abnormal, and shifts the actual axis phase signal used for
control of electric motor 10 from main actual axis phase signal
.theta.d(Main) to auxiliary actual axis phase signal .theta.d(Sub)
(Step S108), and sets the auxiliary sensor diagnosis flag Fs that
is a flag related to abnormality determination for auxiliary motor
rotational position sensor PS2 (Step S109), and outputs a warning
to a driver, namely, warns the driver by turning on the warning
light on the instrument panel of the vehicle (Step S110), and
thereafter terminates the present program.
[0069] In case of YES at Step S104 (auxiliary sensor diagnosis flag
Fs is set), control device 11 determines that abnormality
determination for auxiliary motor rotational position sensor PS2 is
to be performed, and calculates the phase difference
.DELTA..theta.(Sub) between auxiliary actual axis phase signal
.theta.d(Sub) and the control phase by using the equation (1) or
the like (Step S112), and further determines whether or not motor
rotational speed .omega.r is greater than predetermined value
.omega.x (Step S113). In case of NO at Step S113, control device 11
terminates the present program without diagnosis, for prevention of
incorrect diagnosis. On the other hand, in case of YES at Step
S113, control device 11 determines that the diagnosis is to be
continued, and proceeds to Step S114.
[0070] At Step S114, control device 11 determines whether or not
the phase difference .DELTA..theta.(Sub) calculated at Step S112 is
greater than predetermined value .DELTA..theta.x. In case of NO at
Step S114, control device 11 determines that auxiliary motor
rotational position sensor PS2 is not abnormal, and terminates the
present program.
[0071] On the other hand, in case of YES at Step S114, control
device 11 determines that both of main and auxiliary motor
rotational position sensors PS1, PS2 become abnormal, and causes
the failsafe processing part 34 to shut off the steering assist
control system performed by electric motor 10 (Step S115), and
thereafter terminates the present program.
Effects of Action of First Embodiment
[0072] The power steering device configured as described above is
capable of determining abnormality of each motor rotational
position sensor PS1, PS2 by sensor abnormality determination part
49. This serves to enhance safety of the power steering device when
drive control of electric motor 10 is based on each motor
rotational position sensor PS1, PS2.
[0073] Moreover, in the present embodiment, when sensor abnormality
determination part 49 determines abnormality of each motor
rotational position sensor PS1, PS2, the phase difference
.DELTA..theta.(Main), .DELTA..theta.(Sub) is calculated by the
equation as employed for sensorless control, so that it is possible
to perform precise abnormality determination.
[0074] In particular, equations (1)-(3) used in the present
embodiment depend on motor parameters such as resistance r and
inductance Ld of electric motor 10, so that it is possible to
further enhance the precision of abnormality determination.
[0075] The configuration disclosed in patent document 1 where the
electric motor is driven by sensorless control, is already provided
with sensors and others for sensing parameters required to
calculate phase difference .DELTA..theta.. Accordingly, for
application of the present invention to that configuration, it is
sufficient to modify the configuration of control system in
processing unit 22 without provision of additional sensors.
[0076] In the present embodiment, even when main motor rotational
position sensor PS1 becomes abnormal, the drive control of electric
motor 10 by motor drive control part 32 can be continued based on
auxiliary actual axis phase signal .theta.d(Sub) sensed by
auxiliary motor rotational position sensor PS2, so that it is
possible to continue to reduce the driver's steering load.
[0077] Furthermore, in the present embodiment, when drive control
of electric motor 10 is performed by motor drive control part 32
based on auxiliary actual axis phase signal .theta.d(Sub), sensor
abnormality determination part 49 determines whether or not
auxiliary motor rotational position sensor PS2 is abnormal. This
serves to ensure the continuity of the abnormal determination
control, and thereby further enhance safety of the power steering
device.
[0078] In the present embodiment, sensor abnormality determination
part 49 is prevented from determining whether or not each motor
rotational position sensor PS1, PS2 is abnormal, when motor
rotational speed cur estimated from steering speed signal .omega.s
is less than or equal to predetermined value .omega.x, namely, when
a significant error may occur in calculation of phase differences
.DELTA..theta.(Main), .DELTA..theta.(Sub). This serves to prevent
incorrect determination caused by the error in calculation.
[0079] Moreover, in the present embodiment, estimation of motor
rotational speed .omega.r is not based on actual axis phase signals
.theta.d(Main), .theta.d(Sub) outputted by motor rotational
position sensors PS1, PS2 whose abnormalities are to be determined,
but is based on another signal. This serves to correctly determine
whether or not to perform the abnormality determination.
[0080] In particular, in the present embodiment, steering angle
signal .theta.s is employed as another signal, where steering angle
signal .theta.s is a steering angle of the steering wheel whose
motion is linked with motion of electric motor 10 through gears and
others. This makes it easy to estimate motor rotational speed
.omega.r. The feature that the estimation depends on the quantity
of torsion of torsion bar 4 serves to precisely estimate motor
rotational speed .omega.r, even when a deviation occurs between
steering angle signal .theta.s and the rotational position of the
rotor of electric motor 10 with torsion of torsion bar 4.
Second Embodiment
[0081] FIG. 8 is a flow chart showing an abnormality determination
control for motor rotational position sensors PS1, PS2 according to
a second embodiment, which is configured based on the first
embodiment such that when abnormality of main motor rotational
position sensor PS1 is affirmed and the sensor employed for motor
control is shifted to auxiliary motor rotational position sensor
PS2, motor drive control part 32 limits the output of electric
motor 10, for example, by means for reducing the voltage command
value outputted to inverter circuit 24.
[0082] Specifically, in the abnormality determination flow for
motor rotational position sensors PS1, PS2 according to the present
embodiment, in case of NO at Step S114, namely, when it is
determined that phase difference .DELTA..theta.(Sub) between
auxiliary actual axis phase signal .theta.d(Sub) and the control
phase is less than predetermined value .DELTA..theta.x, control
device 11 causes motor drive control part 32 to limit the output of
electric motor 10 (Step S116), and thereafter terminates the
present program.
[0083] In the present embodiment, when main motor rotational
position sensor PS1 becomes abnormal and only auxiliary motor
rotational position sensor PS2 remains normal, constant limitation
of the output of electric motor 10 serves to suppress the steering
load from rapidly increasing when the steering assist force is shut
off based on determination that auxiliary motor rotational position
sensor PS2 is abnormal, and thereby enhance safety of the power
steering device.
Third Embodiment
[0084] FIG. 9 is a flow chart showing an abnormality determination
control for motor rotational position sensors PS1, PS2 according to
a third embodiment, which is configured by replacement of the motor
output limiting operation in the abnormality determination control
according to the second embodiment (Step S116 in FIG. 8) with a
motor output gradually reducing operation (Step S117) for causing
the motor drive control part 32 to gradually reduce the motor
output with time.
[0085] According to the present embodiment, it is possible to
reduce the motor output gradually, and thereby significantly
suppress a driver from feeling uncomfortable about steering with
limitation of the steering assist force, and thereby further
enhance the safety of the power steering device.
Fourth Embodiment
[0086] FIG. 10 is a flow chart showing an abnormality determination
control for motor rotational position sensors PS1, PS2 according to
a fourth embodiment, where the abnormality determination for each
motor rotational position sensor PS1, PS2 by sensor abnormality
determination part 49 is based on comparison between phase
difference .DELTA..theta.(Main) and phase difference
.DELTA..theta.(Sub).
[0087] Specifically, in the abnormality determination control flow
according to the present embodiment, at Steps S201-S203, control
device 11 first performs operations similar to Step S101-S103 in
the flow chart according to the first embodiment.
[0088] Subsequently, control device 11 calculates phase difference
.DELTA..theta.(Main) between main actual axis phase signal
.DELTA.d(Main) and control phase signal .theta.dc, and phase
difference .DELTA..theta.(Sub) between auxiliary actual axis phase
signal .DELTA.d(Sub) and control phase signal .theta.dc (Steps
S204, S205), and thereafter determines whether or not motor
rotational speed .omega.r estimated from steering speed signal WS
is greater than predetermined value .omega.x (Step S206). In case
of NO at Step S206, control device 11 terminates the present
program without diagnosis, for prevention of incorrect diagnosis.
On the other hand, in case of YES at Step S206, control device 11
determines that the diagnosis is to be continued, and proceeds to
Step S207.
[0089] At Step S207, control device 11 determines whether or not a
difference between main phase difference .DELTA..theta.(Main) and
auxiliary phase difference .DELTA..theta.(Sub), which are
calculated at Steps S204, S205, is less than a predetermined value
.DELTA..theta.y. In case of YES at Step S207, control device 11
determines that each motor rotational position sensor PS1, PS2 is
not abnormal, and decrements a motor rotational position sensor
abnormality counter "Cs"(Step S208), and thereafter terminates the
present program.
[0090] On the other hand, in case of NO at Step S207, control
device 11 determines that at least one of motor rotational position
sensors PS1, PS2 becomes abnormal, and proceeds to Step S209. At
Step S209, control device 11 determines whether or no motor
rotational position sensor abnormality counter Cs is greater than a
predetermined value "Cx". In case of NO at Step S209, control
device 11 determines that the abnormality determination is to be
continued, and increments motor rotational position sensor
abnormality counter Cs (Step S212), and thereafter terminates the
present program.
[0091] On the other hand, in case of YES at Step S209, control
device 11 confirms that at least one of motor rotational position
sensors PS1, PS2 is abnormal, and causes failsafe processing part
34 to perform an operation for shifting the steering assist control
system into a safe state by shutoff operation or the like (Step
S210), and further outputs a warning to a driver, namely, warns the
driver by turning on the warning light on the instrument panel of
the vehicle (Step S211), and thereafter terminates the present
program.
[0092] Also in the present embodiment, the power steering device
configured as described above is capable of precisely determining
abnormality of each motor rotational position sensor PS1, PS2 by
sensor abnormality determination part 49. This serves to enhance
safety of the power steering device when drive control of electric
motor 10 is based on each motor rotational position sensor PS1,
PS2.
Fifth Embodiment
[0093] FIGS. 11 to 13 show a power steering device according to a
fifth embodiment of the present invention, which is configured
based on the first embodiment such that sensor abnormality
determination part 49 determines whether or not each motor
rotational position sensor PS1, PS2 is abnormal, depending on a
difference between main actual axis phase signal .theta.m(Main) and
auxiliary actual axis phase signal .theta.m(Sub).
[0094] As shown in FIG. 11, control device 11 according to the
fifth embodiment includes an actual axis phase comparison part 53
in addition to the configuration of the first embodiment, for
comparing main actual axis phase signal .theta.d(Main) with
auxiliary actual axis phase signal .theta.d(Sub).
[0095] Actual axis phase comparison part 53 is configured to
calculate the absolute value of the difference between main actual
axis phase signal .theta.d(Main) and auxiliary actual axis phase
signal .theta.d(Sub) inputted from actual axis phase signal
receiving parts 44a, 44b, and output a result of the calculation
(result of comparison) to sensor abnormality determination part
49.
[0096] Sensor abnormality determination part 49 according to the
present embodiment is configured to determine whether or not main
and auxiliary motor rotational position sensors PS1, PS2 are
abnormal, based on the difference between control phase signal
.theta.dc and main actual axis phase signal .theta.d(Main) or
auxiliary actual axis phase signal .theta.d(Sub), and the result of
comparison outputted from actual axis phase comparison part 53.
[0097] Specifically, sensor abnormality determination part 49
determines that the corresponding motor rotational position sensor
PS1 (PS2) is abnormal, in response to a condition that the absolute
value of the difference between main actual axis phase signal
.theta.d(Main) and auxiliary actual axis phase signal .theta.d(Sub)
outputted from actual axis phase comparison part 53 is greater than
a predetermined value .theta.z, and phase difference
.DELTA..theta.(Main), .DELTA..theta.(Sub) is greater than
predetermined value .DELTA..theta.x.
[0098] Sensor abnormality determination part 49 is further
configured to: be prevented from determining abnormality of
auxiliary motor rotational position sensor PS2 in a situation where
the system shifts from a state where motor drive control part 32
controls electric motor 10 based on main actual axis phase signal
.theta.d(Main) to a state where motor drive control part 32
controls electric motor 10 based on auxiliary actual axis phase
signal .theta.d(Sub); and immediately after a predetermined time
period elapses, restart the abnormality determination.
[0099] FIGS. 12 and 13 are flow charts showing the abnormality
determination control for motor rotational position sensors PS1,
PS2 according to the present embodiment.
[0100] As shown in FIG. 12, in the present embodiment, at Steps
S301-S303, control device 11 performs operations similar to Steps
S101-S103 in the flow chart of the first embodiment. Subsequently,
at Step S304, control device 11 determines whether or not a main
sensor diagnosis flag "Fm", which is set at Step S314 described
below, or an auxiliary sensor diagnosis flag "Fs", which is set at
Step S317 described below, is set. In case of NO at Step S304
(neither is set), control device 11 proceeds to Step S305.
[0101] At Step S305, control device 11 determines whether or not
the absolute value of the difference between main actual axis phase
signal .theta.d(Main) and auxiliary actual axis phase signal
.theta.d(Sub) calculated by actual axis phase comparison part 53 is
greater than predetermined value .theta.z. In case of NO at Step
S305, control device 11 determines that both of motor rotational
position sensors PS1, PS2 are normal, and clears motor rotational
position sensor abnormality counter Cs (Step S321), and thereafter
terminates the present program.
[0102] On the other hand, in case of YES at Step S305, control
device 11 increments the motor rotational position sensor
abnormality counter Cs (Step S306), and thereafter determines
whether or not motor rotational position sensor abnormality counter
Cs is greater than predetermined value Cx (Step S307). In case of
NO at Step S307, control device 11 terminates the present program,
without confirmation of the abnormality.
[0103] On the other hand, in case of YES at Step S307, control
device 11 confirms that at least one of motor rotational position
sensors PS1, PS2 becomes abnormal, and thereafter performs Step
S308 and the following operations for confirming which one of motor
rotational position sensors PS1, PS2 is abnormal.
[0104] That is implemented by calculating the main phase difference
.DELTA..theta.(Main) (Step S308), and thereafter determining
whether or not motor rotational speed .omega.r estimated from
steering speed signal .omega.s is greater than predetermined value
.omega.x (Step S309).
[0105] In case of NO at Step S309, since it is difficult to
determine which one of motor rotational position sensors PS1, PS2
is failed, control device 11 causes failsafe processing part 34 to
shut off the steering assist control system (Step S319), and
further outputs a warning to a driver, namely, warns the driver by
turning on the warning light on the instrument panel of the vehicle
(Step S320), and thereafter terminates the present program.
[0106] On the other hand, in case of YES at Step S309, control
device 11 determines whether or not main phase difference
.DELTA..theta.(Main) is greater than predetermined value
.DELTA..theta.x (Step S310).
[0107] In case of YES at Step S310, control device 11 determines
that main motor rotational position sensor PS1 becomes failed, and
shifts the actual axis phase signal from main actual axis phase
signal .theta.d(Main) to auxiliary actual axis phase signal
.theta.d(Sub) for the motor drive control (Step S311), and clears a
stabilization timer counter "Tset" (Step S312), and sets auxiliary
sensor diagnosis flag Fs (Step S313), and resets main sensor
diagnosis flag Fm (Step S314), and outputs a warning to a driver
(Step S315), and terminates the present program.
[0108] On the other hand, in case of NO at Step S310, control
device 11 determines that auxiliary motor rotational position
sensor PS2 becomes failed, and resets auxiliary sensor diagnosis
flag Fs (Step S316), and sets main sensor diagnosis flag Fm (Step
S317), and outputs a warning to a driver (Step S318), and
terminates the present program.
[0109] In case of YES at Step S304, namely, when at least one of
main and auxiliary motor rotational position sensors PS1, PS2
becomes abnormal, and main sensor diagnosis flag Fm or auxiliary
sensor diagnosis flag Fs is set, control device 11 proceeds to Step
S322 shown in FIG. 13.
[0110] At Step S322, control device 11 determines whether or not
auxiliary sensor diagnosis flag Fs is set. In case of YES at Step
S322, control device 11 determines whether or not stabilization
timer counter Tset is greater than a predetermined value Tx (Step
S323). In case of NO at Step S323, control device 11 increments the
stabilization timer counter Tset (Step S328), and thereafter
terminates the present program.
[0111] On the other hand, in case of YES at Step S323, namely, when
it is determined that the predetermined time period has elapsed
after the motor rotational position sensor employed for motor drive
control is shifted from main motor rotational position sensor PS1
to auxiliary motor rotational position sensor PS2, control device
11 calculates auxiliary phase difference .DELTA..theta.(Sub) (Step
S324), and further determines whether or not motor rotational speed
.omega.r is greater than predetermined value .omega.x (Step S325).
In case of NO at Step S325, control device 11 terminates the
present program without diagnosis, for prevention of incorrect
diagnosis. On the other hand, in case of YES at Step S325, control
device 11 determines that the diagnosis is to be continued, and
proceeds to Step S326.
[0112] At Step S326, control device 11 determines whether or not
auxiliary phase difference .DELTA..theta.(Sub) calculated at Step
S324 is greater than predetermined value .DELTA..theta.x. In case
of NO at Step S326, control device 11 determines that no
abnormality occurs in auxiliary motor rotational position sensor
PS2, and terminates the present program.
[0113] On the other hand, in case of YES at Step S326, control
device 11 determines that both of main and auxiliary motor
rotational position sensors PS1, PS2 become abnormal, and causes
failsafe processing part 34 to shut off the steering assist control
system based on electric motor 10 (Step S327), and thereafter
terminates the present program.
[0114] In case of NO at Step S322, control device 11 calculates
main phase difference .DELTA..theta.(Main) (Step S329), and
thereafter determines whether or not motor rotational speed
.omega.r is greater than predetermined value .omega.x (Step S330).
In case of NO at Step S330, control device 11 terminates the
present program without diagnosis, for prevention of incorrect
diagnosis. On the other hand, in case of YES at Step S330, control
device 11 determines that the diagnosis is to be continued, and
proceeds to Step S331.
[0115] At Step S331, control device 11 determines whether or not
main phase difference .DELTA..theta.(Main) calculated at Step S329
is greater than predetermined value .DELTA..theta.x. In case of NO
at Step S331, control device 11 determines that no abnormality
occurs in main motor rotational position sensor PS1, and terminates
the present program.
[0116] On the other hand, in case of YES at Step S331, control
device 11 determines that both of main and auxiliary motor
rotational position sensors P51, PS2 become abnormal, and causes
failsafe processing part 34 to shut off the steering assist control
system based on electric motor 10 (Step S332), and thereafter
terminates the present program.
[0117] Also in the present embodiment configured as described
above, it is possible to determine precisely by sensor abnormality
determination part 49 whether or not each motor rotational position
sensor PS1, PS2 is abnormal.
[0118] In the present embodiment, the feature that sensor
abnormality determination part 49 determines abnormality of each
motor rotational position sensor P51, PS2 depending on a result of
comparison between main and auxiliary actual axis phase signals
.theta.d(Main), .theta.d(Sub) outputted by main and auxiliary motor
rotational position sensors PS1, PS2, serves to enhance the
precision of abnormality determination.
[0119] In particular, the feature that it determines that main
motor rotational position sensor PS1 is abnormal, when actual axis
phase signal .theta.d(Main) outputted by main motor rotational
position sensor PS1 is significantly apart from both of actual axis
phase signal .theta.d(Sub) outputted by auxiliary motor rotational
position sensor PS2 and control phase signal .theta.dc, serves to
enhance the precision of abnormality determination for main motor
rotational position sensor PS1.
[0120] In the present embodiment, the feature that sensor
abnormality determination part 49 is configured to be prevented
from determining abnormality of auxiliary motor rotational position
sensor PS2 immediately after the motor rotational position sensor
employed for drive control of electric motor 10 is shifted from
main motor rotational position sensor PS1 to auxiliary motor
rotational position sensor PS2, serves to suppress determination
based on auxiliary actual axis phase signal .theta.d(Sub) before
auxiliary motor rotational position sensor PS2 is completely
started up, and thereby further suppress incorrect
determination.
[0121] The present invention is not limited to the configurations
of the embodiments described above. Specific configuration of the
present invention may be modified in accordance with device
specifications without going out of the substance of the present
invention.
[0122] The power steering devices and the power steering device
control devices according to the embodiments described above can be
implemented by the following modes, for example.
[0123] According to one mode, a power steering device control
device for a power steering device, the power steering device
including: a steering mechanism configured to transmit rotation of
a steering wheel to a steered wheel; an electric motor configured
to apply a steering assist force to the steering mechanism; a
transmission mechanism disposed between the steering mechanism and
the electric motor, and configured to transmit a torque of the
electric motor to the steering mechanism; and a first motor
rotational position sensor configured to sense as an actual axis
phase a rotational position of a rotor of the electric motor; the
power steering device control device includes: an actual axis phase
signal receiving part configured to receive input of a signal of
first actual axis phase outputted from the first motor rotational
position sensor; a motor current signal receiving part configured
to receive input of a signal of value of electric current flowing
through the electric motor; a control phase estimation part
configured to estimate as a control phase a phase of an induced
voltage occurring in the electric motor, based on the signal of
value of electric current; and a sensor abnormality determination
part configured to determine whether or not the first motor
rotational position sensor is abnormal, based on a difference
between the first actual axis phase and the control phase.
[0124] According to a preferable mode, the power steering device
control device is configured such that: the power steering device
further includes a second motor rotational position sensor
configured to sense as an actual axis phase the rotational position
of the rotor of the electric motor; the power steering device
control device further includes a motor drive control part
configured to control driving of the electric motor, based on the
signal of first actual axis phase; and the motor drive control part
is configured to control driving of the electric motor, based on an
output signal of the second motor rotational position sensor as a
signal of second actual axis phase, in response to a determination
that the first motor rotational position sensor is abnormal.
[0125] According to another preferable mode, the power steering
device control device according to one of the modes described above
further includes an actual axis phase comparison part configured to
compare the signal of first actual axis phase with the signal of
second actual axis phase, wherein the sensor abnormality
determination part is configured to determine whether or not the
first motor rotational position sensor is abnormal, based on the
difference between the first actual axis phase and the control
phase, and a result of the comparison by the actual axis phase
comparison part.
[0126] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to determine that the first motor rotational position
sensor is abnormal, in response to a condition that a difference
between the signal of first actual axis phase and the signal of
second actual axis phase is greater than a predetermined value, and
the difference between the first actual axis phase and the control
phase is greater than a predetermined value.
[0127] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to determine whether or not the second motor
rotational position sensor is abnormal, based on a difference
between the second actual axis phase and the control phase, when
the motor drive control part is controlling driving of the electric
motor based on the signal of second actual axis phase.
[0128] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to start to determine whether or not the second motor
rotational position sensor is abnormal, in response to a lapse of a
predetermined time period after the motor drive control part shifts
from the drive control based on the signal of first actual axis
phase to the drive control based on the signal of second actual
axis phase.
[0129] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to determine whether or not the second motor
rotational position sensor is abnormal, based on a difference
between the second actual axis phase and the control phase, when
the motor drive control part is controlling driving of the electric
motor based on the signal of second actual axis phase.
[0130] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the motor drive control part is configured
to control driving of the electric motor such that output of the
electric motor decreases, after shifting from the drive control
based on the signal of first actual axis phase to the drive control
based on the signal of second actual axis phase.
[0131] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the motor drive control part is configured
to control driving of the electric motor such that output of the
electric motor decreases gradually, after shifting from the drive
control based on the signal of first actual axis phase to the drive
control based on the signal of second actual axis phase.
[0132] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to determine whether or not the first motor
rotational position sensor is abnormal, based on comparison between
the difference between the first actual axis phase and the control
phase and a difference between the second actual axis phase and the
control phase.
[0133] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to stop determining whether or not the first motor
rotational position sensor is abnormal, in response to a condition
that rotational speed of the electric motor is less than or equal
to a predetermined value.
[0134] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the rotational speed of the electric motor
is configured to be estimated based on a signal other than the
signal outputted from the first motor rotational position
sensor.
[0135] According to another preferable mode, the power steering
device control device according to one of the modes described above
further includes a steering angle signal receiving part configured
to receive input of a signal of rotational angle of the steering
wheel as steering angle, wherein the rotational speed of the
electric motor is configured to be estimated based on the signal of
steering angle.
[0136] According to another preferable mode, the power steering
device control device according to one of the modes described above
further includes: a torsion bar provided in the steering mechanism;
and a steering angle sensor disposed closer to the steering wheel
than the torsion bar, and configured to sense the steering angle;
wherein the rotational speed of the electric motor is configured to
be estimated depending on a quantity of torsion of the torsion
bar.
[0137] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to: calculate the difference between the first actual
axis phase and the control phase, based on a voltage (Vdc) in a
d-axis, a voltage (Vqc) in a q-axis, a sensed electric current
(Idc) in the d-axis, a sensed electric current (Iqc) in the q-axis,
and a rotational speed (.omega.1) of the control phase, wherein the
d-axis is a pole-to-pole direction of the rotor of the electric
motor, and wherein the q-axis is perpendicular to the d-axis; and
determine whether or not the first motor rotational position sensor
is abnormal, based on a result of the calculation of the
difference.
[0138] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to calculate the difference between the first actual
axis phase and the control phase, further depending on a resistance
(r) of winding of the electric motor and an inductance (Lq) of the
electric motor.
[0139] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to calculate the difference between the first actual
axis phase and the control phase by using the following
equation:
.DELTA. .theta. = tan - 1 [ Vdc - r Idc + .omega. 1 Lq Iqc Vqc - r
Iqc - .omega. 1 Lq Idc ] . ##EQU00004##
[0140] According to another preferable mode, the power steering
device control device according to one of the modes described above
is configured such that the sensor abnormality determination part
is configured to calculate the difference between the first actual
axis phase and the control phase by using the following
equation:
.DELTA. .theta. = tan - 1 [ Idc - r Vdc + .omega. 1 Lq Vqc Iqc - r
Vqc - .omega. 1 Lq Vdc ] . ##EQU00005##
[0141] According to one mode, a power steering device includes: a
steering mechanism configured to transmit rotation of a steering
wheel to a steered wheel; an electric motor configured to apply a
steering assist force to the steering mechanism; a transmission
mechanism disposed between the steering mechanism and the electric
motor, and configured to transmit a torque of the electric motor to
the steering mechanism; a first motor rotational position sensor
configured to sense as an actual axis phase a rotational position
of a rotor of the electric motor; and a control device configured
to control driving of the electric motor; the control device
including: an actual axis phase signal receiving part configured to
receive input of a signal of first actual axis phase outputted from
the first motor rotational position sensor; a motor current signal
receiving part configured to receive input of a signal of value of
electric current flowing through the electric motor; a control
phase estimation part configured to estimate as a control phase a
phase of an induced voltage occurring in the electric motor, based
on the signal of value of electric current; and a sensor
abnormality determination part configured to determine whether or
not the first motor rotational position sensor is abnormal, based
on a difference between the first actual axis phase and the control
phase.
[0142] According to a preferable mode, the power steering device is
configured such that: the power steering device further includes a
second motor rotational position sensor configured to sense as an
actual axis phase the rotational position of the rotor of the
electric motor; the control device further includes a motor drive
control part configured to control driving of the electric motor,
based on the signal of first actual axis phase; and the motor drive
control part is configured to control driving of the electric
motor, based on an output signal of the second motor rotational
position sensor as a signal of second actual axis phase, in
response to a determination that the first motor rotational
position sensor is abnormal.
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